Many administrators have trouble with getting passive working. There is a good article over on TechNet (http://technet.microsoft.com/en-us/library/dd421710(v=ws.10).aspx) that works well if you’re using the local FTP services built into IIS.
There are slight modifications if you are using Gene6FTP Server.
The only thing you really have to do is add G6FTPServer.exe to the allowed programs inbound rules. Assuming your outbound is always “allow”.
New Inbound Rule, Program, point to C:\Program Files (x86)\Gene6 FTP Server\G6FTPServer.exe
That should fix your Passive (PASV) mode.
If you want to limit what ports to use, you can right click on the domain and properties. Under “IP binding” you can limit what ports to use.
Without this, you will get errors such as in Visual Studio when trying to use FTP, that a connection failed due to 425 error. Or Can’t open a data connection (425).